HALIFAX (CP) — Lettuce used at KFC and Taco Bell outlets is the likely source of a recent outbreak of gastro-intestinal illness caused by E. coli bacteria in Nova Scotia, New Brunswick and Ontario, a health official said Friday.

“The feeling is that it’s a common source across all three provinces,” said Dr. Frank Atherton, Nova Scotia’s deputy chief medical officer.

The fast-food outlets are not believed to be the responsible for the contamination, and neither is the Ontario-based firm that distributed the lettuce, he added.

Atherton said KFC and Taco Bell outlets have been inspected, but he didn’t know how many.

“We don’t believe there’s a problem in the KFC/Taco Bell outlets themselves,” he said. “The problem is really in the food that’s been distributed.”

Atherton said it’s unlikely that more E. coli cases will be reported because the lettuce in question has passed its shelf-life and is probably out of the food chain.

“We’re not seeing new cases,” he said, noting that the most recent case in Nova Scotia was recorded Jan. 2.

“If there was infected material still being served in restaurants we would expect to continue to see cases. At the moment, we’re not, but we remain vigilant.”

As an added precaution, the Canadian Food Inspection Agency is recalling the lettuce believed to be at the centre of the outbreak.

Atherton said none of the lettuce in question was shipped to grocery stores.

The federal government is continuing to investigate the cause of the contamination, which means inspectors are now looking farther up the food chain at farms.

New Brunswick has reported six cases of the infection, Nova Scotia has had 10 and there have been at least four cases in Ontario.

At least one infected woman is still recovering in hospital in Nova Scotia.

Symptoms of the gastro-intestinal illness include severe cramps, bloody diarrhea and vomiting.